Steering systems are typically tuned by engineers holding a steering wheel (also referred to as a handwheel) with two hands in a symmetric grip pattern (e.g., 9/3 o'clock or 10/2 o'clock hand positions). However, in operation, drivers often adapt the grip patterns for comfort which can result in asymmetric grip patterns. Such an asymmetric grip pattern often results in a bias torque on the handwheel due to the weight of the driver's arm acting on the rim of the handwheel with unbalanced moment arms. This bias torque is very similar to the steering pull due to chassis/tire imbalances. The unbalance has to be compensated by the arm muscles of the driver and can result in driver fatigue over longer times/distances.
Another situation occurs when a driver shifts from two-handed to one-handed driving. This can take place either due to arm fatigue or because the driver is performing another task with the free hand, e.g., holding a beverage cup, operating an infotainment system, etc. A steering system tuned for two-handed driving can be significantly more fatiguing to drive with one hand, as the force required in a single hand has to be doubled to produce the same input shaft torque.